Gas burners are widely used in furnaces, boilers and other heating apparatuses used to generate heat for residential and commercial use. Such burners come in myriads of designs, but at their core, they all serve the basic function of igniting gas (typically natural gas) and air, and directing the resulting combustion gases to a heat exchanger. The combustion gases are at an elevated temperature and by directing those through serpentine conduits provided as part of the heat exchanger, the heat exchanger coils are heated. Air to be heated can then be directed across the heat exchanger coils to extract that heat. The heated air can then be communicated through ductwork to the rooms or space needing to be heated.
Typically, the air and gas is ignited by an igniter provided within or immediately aft of the burner. Modern furnaces, however, often include multiple burners with one being associated with each conduit of the heat exchanger. Alternatively, for efficiency purposes, a separate igniter may not be provided with each burner, but rather only one burner may include an igniter, and once that burner achieves combustion, the resulting flame is communicated or transferred to adjacent burners.
The current industry standard for holding and stabilizing the flame is referred to as an “in-shot” burner. The in-shot burner uses a small channel between flameholders to enable a small flame to transfer sufficient heat to light each successive burner. While effective, such prior art burners require a secondary air gap between the in-shot burner outlet and an inlet to the heat exchanger. Current environmental regulations and consumer demands, however, are requiring increasingly stringent burner emissions, including nitrogen oxide (NOx) emissions. In order to meet those reduced emission standards, that secondary air gap must be eliminated, and thus so too must the in-shot burner approach. Fully pre-mixed burners allow for combustion without a secondary air source at the igniter, but there is currently no way to transfer ignition between burners.
Accordingly, a need exists for a mechanism and method for lighting successive burners in a multi-burner heat exchanger assembly using a fully premixed heating system.